In a “transfer-hydrogenation,” a “hydrogen donor” provides a H2-equivalent that is transferred to a recipient. This reaction is illustrated below for the transfer of hydrogen from an alcohol to an aldehyde or ketone.

Because the reactants and the products are both a mixture of alcohols and carbonyls, the reaction equilibrium may be modest and can limit the conversion. It has been common in the art of transfer-hydrogenation to employ a large excess of the donor alcohol to favor higher conversion of the acceptor to the saturated alcohol product. The excess alcohol, however, leads to added expense, which is required to separate, recover, and recycle the donor alcohol.
Thus, there is a need for a more economical and efficient transfer-hydrogenation process, particularly one that does not require a large excess of the donor alcohol.
The present invention addresses this need as well as others, which will become apparent from the following description and the appended claims.